The present invention relates generally to diaphragm clutches, particularly for motor vehicles, such clutches being of the kind in which the resilient means provided for their engagement consists of an annular member, known as a diaphragm, which comprises a peripheral portion forming a conical plate spring integral with a central portion divided into fingers by radially-directed slots.
In order to release clutches of this kind it is necessary to apply a disengaging force to the ends of the radial fingers of the diaphragm using a disengaging member, usually called a release bearing assembly.
A release bearing assembly of this kind generally contains a ball bearing serving to separate, in respect of rotation, that member of the assembly which is intended to act on the diaphragm and which is usually called the actuating member, from the member, usually called the control member, which is adapted to be operated for this purpose by a release mechanism, which is usually a clutch release yoke; the assembly is designed to act on diaphragm either by thrust or by traction.
When it acts by thrust, one of the rings of the bearing, forming the actuating member, may very simply bear directly against the ends of the fingers of the diaphragm.
However, in practice, since the diaphragm is generally flat when the clutch containing it is in the position of engagement and if the friction linings of its friction disc are in new condition, toric contact is desirable between this bearing ring and the diaphragm fingers because of the conical shape assumed by them through flexion when their ends are subjected to an axial thrust applied by the bearing ring. For this purpose the fingers of the diaphragm may have a rounded boss at their ends.
This arrangement, which has the advantage of permitting the use of a bearing having a plane actuating edge, has the disadvantage of requiring the application of a special configuration to the ends of the diaphragm fingers.
As an alternative, the ends of the diaphragm fingers may be plane, but the actuating edge of the bearing must then itself be torically rounded.
In either case, difficulties may arise on the occasion of an overhaul or rebuilding of a clutch entailing the changing of the diaphragm, if the diaphragm available for this change is not suitable for the clutch release bearing fitted.
It is therefore desirable, particularly in cases of this kind, to have a part available which for the sake of convenience will be called an operating member, and which, when attached to the ends of the diaphragm fingers, accommodates the bending of the latter during operation, while offering to the corresponding clutch release bearing a plane support surface.
When the clutch release bearing acts by traction on the clutch diaphragm, it is necessary for it to have an annular collar, which for the sake of convenience will be called a support collar or ring, and which is disposed axially on the other side of the diaphragm, or for it to be axially fastened to an operating member having a support collar of this kind.
An operating member of this kind usually forms one of the components of the clutch release bearing, and this results in a certain overall complexity of the latter.
It is therefore desirable to be able to have available an operating member which, when attached independently on the ends of the fingers of a diaphragm, is then adapted to be axially connected to a clutch release bearing in order to enable the latter to act by traction on the diaphragm.
In French patent application filed on Mar. 24, 1972 under No. 72 11145 and published under No. 2.131.731, a diaphragm clutch is described, on the diaphragm of which an operating member of this kind is permanently attached in order to operate a withdrawal member, which in this particular case is reduced to a thrust rod serving as clutch release bearing.
This operating member comprises on the one hand, on a first side of the diaphragm, a support collar applied against the diaphragm by a support face and on the other hand, on the other side of the diaphragm, retaining shoulders adapted to secure it axially to the latter.
However, the retaining shoulders are formed thereon by the ends of elastically deformable tongues which, being parts separate from the operating member itself, are each individually attached on the latter by suitable fastening means.
This results in a relatively complex arrangement, which is therefore expensive, while it is also possible for the retaining shoulders to become detached from the diaphragm fingers against which they bear, through the rotation about their fastening means of the elastically deformable tongues on which they are formed.
In addition, although for the purposes of placing an operating member of this kind in position on the diaphragm to which it is to be fitted it is sufficient to present this member axially in front of the diaphragm in such a manner that the elastically deformable tongues provided on it are in line with the slots in the diaphragm and can thus pass axially through the latter, and then to turn this operating member about the axis of the assembly until these elastically deformable tongues are engaged on the fingers of the diaphragm, it is necessary in practice, because of the circumferential extent of the ends of these elastically deformable tongues forming the retaining shoulders, to widen accordingly those slots in the diaphragm in which they are to be engaged.
The consequence is that the fingers of the diaphragm do not all have the same configuration at their ends, and that therefore they do not all work under the same conditions, which is prejudicial to the whole arrangement.
In French Pat. No. 1595078 of the Dec. 13, 1968 a clutch diaphragm equipped with an operating member is described.
Although in this French patent the operating member has the advantage of being in one piece, the retaining shoulders provided on it being integral with its support collar, the entire member, comprising the support collar and the retaining shoulders, extends on the same side of the diaphragm, so that those fingers of the diaphragm which are in engagement with the retaining shoulders are permanently bent.
The placing in position of an operating member of this kind in fact makes it necessary, after the diaphragm and the operating member have been brought sufficiently close to one another, for the ends of as many diaphragm fingers as there are retaining shoulders on the operating member to be bent relative to the others in the axial direction, and then for the operating member to be turned circumferentially about the axis of the assembly, relative to the diaphragm, while at the end of this rotation those diaphragm fingers which have been engaged with the retaining shoulders of the operating member are prevented by the latter from returning to their original natural configuration.
Apart from the fact that in the zone in which these fingers merge into the peripheral diaphragm portion forming the conical spring plate this results in an inopportune modification of the distribution of stresses in the peripheral portion, the operating conditions of which are liable to be disturbed thereby, these fingers are prevented from suitably participating in the axial clutch release force which has to be transmitted when the clutch is disengaged, to the detriment of the efficiency of the whole arrangement.
Moreover, because the retaining shoulders are disposed at the bottom of cutouts leading out onto the support force of the support collar for penetration into the said cutouts of those fingers of the diaphragm which are to cooperate with the said retaining shoulders, the said support force of the support collar is discontinuous to the detriment of the rigidity of the latter and the extent of its surface of contact with the diaphragm, and the axial dimensions of the whole arrangement are relatively large.
The general object of the present invention is an arrangement which enables these aforesaid disadvantages to be avoided.